【计蒜课】【数据结构】【栈的复习】
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#define ERROR 0
#define OK 1
typedef struct Stack {
int *elements;
int max_size, top_index;
} Stack;
void init(Stack *s,int length) {
s->elements = (int *)malloc(sizeof(int) * length);
s->max_size = length;
s->top_index = -1;
}
int push(Stack *s,int element) {
if (s->top_index >= s->max_size - 1) {
return ERROR;
}
s->top_index++;
s->elements[s->top_index] = element;
return OK;
}
int pop(Stack *s) {
if (s->top_index < 0) {
return ERROR;
}
s->top_index--;
return OK;
}
int top(Stack *s) {
return s->elements[s->top_index];
}
int empty(Stack *s) {
if (s->top_index < 0) {
return 1;
} else {
return 0;
}
}
int precede(char a,char b) {
if(a=='*' || a=='/'){
if(b=='*' || b=='/')
return 0;
else
return 1;
}
else
return 0;
}
int operate(char theta,int a,int b) {
if (theta == '+') {
return a + b;
}
if(theta == '-'){
return b - a;
}
if(theta == '/'){
return b / a;
}
else {
return a * b;
}
}
void calc(Stack *numbers, Stack *operators) {
int a=top(numbers);
pop(numbers);
int b=top(numbers);
pop(numbers);
push(numbers,operate(top(operators),a,b));
pop(operators);
}
void clear(Stack *s) {
free(s->elements);
free(s);
}
int main() {
int m;
scanf("%d",&m);
Stack *numbers=(Stack*)malloc(sizeof(Stack));
init(numbers,m);
Stack *operators=(Stack*)malloc(sizeof(Stack));
init(operators,m);
char *buffer=(char*)malloc(sizeof(char)*(m+1));
scanf("%s",buffer);
int i=0;
while(i<m){
if(isdigit(buffer[i])){
push(numbers,buffer[i]-'0');
i++;
}else{
if(empty(operators) || precede(buffer[i],top(operators))){
push(operators,buffer[i]);
i++;
}
else{
calc(numbers,operators);
}
}
}
while(!empty(operators)){
calc(numbers,operators);
}
printf("%d\n",top(numbers));
clear(numbers);
clear(operators);
free(buffer);
return 0;
}
